title: Mild hypothermia delays the development of stone heart from untreated sustained ventricular fibrillation--a cardiovascular magnetic resonance study.
abstract: BACKGROUND
  'Stone heart' resulting from ischemic contracture of the myocardium, precludes successful resuscitation from ventricular fibrillation (VF). We hypothesized that mild hypothermia might slow the progression to stone heart.
  
  
  METHODS
  Fourteen swine (27 ± 1 kg) were randomized to normothermia (group I; n=6) or hypothermia groups (group II; n=8). Mild hypothermia (34 ± 2 °C) was induced with ice packs prior to VF induction. The LV and right ventricular (RV) cross-sectional areas were followed by cardiovascular magnetic resonance until the development of stone heart. A commercial 1.5T GE Signa NV-CV/i scanner was used. Complete anatomic coverage of the heart was acquired using a steady-state free precession (SSFP) pulse sequence gated at baseline prior to VF onset. Un-gated SSFP images were obtained serially after VF induction. The ventricular endocardium was manually traced and LV and RV volumes were calculated at each time point.
  
  
  RESULTS
  In group I, the LV was dilated compared to baseline at 5 minutes after VF and this remained for 20 minutes. Stone heart, arbitrarily defined as LV volume <1/3 of baseline at the onset of VF, occurred at 29 ± 3 minutes. In group II, there was less early dilation of the LV (p<0.05) and the development of stone heart was delayed to 52 ± 4 minutes after onset of VF (P<0.001).
  
  
  CONCLUSIONS
  In this closed-chest swine model of prolonged untreated VF, hypothermia reduced the early LV dilatation and importantly, delayed the onset of stone heart thereby extending a known, morphologic limit of resuscitability.
authors.affiliation: Department of Medicine, Sarver Heart Center, University of Arizona College of Medicine, Tucson, Arizona, USA. vsorrell@email.arizona.edu
authors.forename: Vincent L
authors.initials: VL
authors.lastname: Sorrell
authors.forename: Vijayasree
authors.initials: V
authors.lastname: Paleru
authors.forename: Maria I
authors.initials: MI
authors.lastname: Altbach
authors.forename: Ronald W
authors.initials: RW
authors.lastname: Hilwig
authors.forename: Karl B
authors.initials: KB
authors.lastname: Kern
authors.forename: Mohamed
authors.initials: M
authors.lastname: Gaballa
authors.forename: Gordon A
authors.initials: GA
authors.lastname: Ewy
authors.forename: Robert A
authors.initials: RA
authors.lastname: Berg
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D006323:Heart Arrest / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D017379:Hypertrophy, Left Ventricular / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D007036:Hypothermia, Induced; D008279:Magnetic Resonance Imaging; D011897:Random Allocation; D013552:Swine; D013997:Time Factors; D014693:Ventricular Fibrillation / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D016277:Ventricular Function, Left; D016278:Ventricular Function, Right